Frequently Asked Questions - Naked Filter

Frequently Asked Questions


How do I use the bottle?

It works just like most sports water bottles. Fill the bottle from any fresh water source, screw on the cap tightly, and drink! It’s that simple. 

How do I get the best flow through the filter?

To get the best flow rate out of your bottle, make sure you are squeezing the bottle in the area where you get the most flexibility. Squeeze the bottle while you suck on the mouthpiece. With a new filter, the flow can increase slightly as you use the first 5-10 bottles of water.

How do I replace (remove/install) the filter cartridge?

Change the filter when you feel the flow rate has become too slow. Remove the old filter then Install and Condition a new filter according to the instructions in the User Guide.

How long does a filter last?

The Naked Filter will let you know when it’s finished and needs to be replaced! The water flow rate will slow over the life of the filter, if pushed to the limit, it will eventually not let any water through at all. In our testing, with moderately challenging water, the filter lasts 20-30 gallons before the flow rate slows significantly. We consider this the end of life of the filter, although you certainly can use the filter for as long as water flows through it. The filter is equally as effective at reducing microorganisms at the very last drop as it is at the very first drop. That fail-safe efficacy will not diminish over time. Do keep in mind that the capacity of a filter will vary based on the composition of the water you filter through it. Water with higher turbidity levels (murkier water) will shorten the life of your filter, because the filter will snare more particles during each use. We always recommend using the clearest source of water that you have available.

How many disposable water bottles can I save by using Naked Filter instead?

Assuming a 30 gallon life of one Naked Filter cartridge, that would save about 228 16.9 oz standard disposable water bottles. By getting naked you are avoiding the waste of A LOT of plastic.

Does the cap fit other bottles?

Yes indeed it does. We designed the Naked Filter cap to fit a common generic 63 mm sport water bottle mouth. In the spirit of, ‘reduce, recycle, re-use,’ we encourage you to use the cap and filter with a bottle you currently own. Whether you use one of our bottles or a generic bottle you already own, please do make sure the cap has a good seal to the bottle you use. The cap will NOT fit ALL sport water bottle mouths. There are a lot of slight design variations in the bottle dimensions and threads. Any leaks could lead to you accidentally drinking unsafe water that hasn’t passed through the filter. For example, the cap may fit a standard wide mouth Nalgene® bottle and the Specialized® Purist 26 oz bottle, but we cannot make any representations concerning the general performance when used on bottles from other manufacturers. 

Can I store the filter after initial use and reuse it later?

Sure. We do, however, recommend treating it first with a solution of bleach and water to disinfect the filter and prevent the growth of microorganisms while in storage. Put two drops of bleach in bottle, then fill the bottle with water. Put the cap on and squeeze the bottle 3 or 4 times. Allow the filter and the bottle to air dry overnight. Once the filter is dry, place it in a sealable plastic bag. Store at room temperature out of direct sunlight.

Can I put Naked Filter in the dishwasher?

We do not recommend putting any parts of Naked Filter in the dishwasher. Doing so might damage a part. We do recommend at least occasionally hand-washing using soap and water to clean the cap and the bottle.

Can I put Naked Filter in the microwave or freezer?

Don’t do it. That would be a bad idea!

What are the recommended water temperatures?

We recommend water temperatures between a maximum of 90F / 30C and a minimum of 40F / 5C. We recommend not leaving the bottle inside a hot car for extended periods.

Can I use ice water with Naked Filter?

Yes, you can. There is no danger caused by adding ice to the water in the bottle. However, please be aware that the flow rate of the water through the filter may noticeably slow when using very cold water. Cold water is more viscous than room temperature water and thus tends to flow more slowly through the membrane structure. Please keep in mind the above recommend water temperatures.

Can I filter other liquids besides water – like juice, coffee or tea - with the Naked Filter?

You could, but we certainly don’t recommend it! The filter is intended to be used only for filtering drinking water.

Can I drink urine out of Naked Filter?

No! We certainly do not recommend that. But if you are so inclined, we can’t stop you!

Can I drink salt water (sea water) out of Naked Filter?

No! The Naked Filter is awesome, but it cannot remove salt from water. That process requires much tighter membranes (like reverse osmosis membranes), and a huge amount of water pressure or energy.

Can I clean the filter?

No you can’t. Sorry, but Naked Filter’s nanofiber membrane is not cleanable. See the procedure for storing the filter. Microorganisms and other particles become lodged in the nanofiber structure and do not wash out. Attempting to wash the filter might damage it and thereby render it ineffective.

How should I dispose of a used filter?

Used filters should be disposed of in the trash. Our filter cartridge is not recyclable.

What is the shelf-life of an unused filter?

When kept sealed, the shelf life is at least 3 years.

Technology, Materials, and Health

What is the membrane made of?

The membrane is made of polyacrylonitrile or PAN. This is a food grade plastic that is commonly used.

Does the filter add any chemicals to the water?

No it does not. This is a mechanical filter that physically separates contaminants from the water.

Is the Naked Filter BPA free?

Yes it is. In addition, all materials we work with are food grade materials.

How fast does the water flow through Naked Filter?

When using a combined squeeze and suck drinking technique you should get a satisfying mouthful with each drink. As the water level in the bottle decreases, you generate less pressure with each squeeze, so the the flow rate tends to decrease slightly. There is a less noticeable decrease if you tend to suck rather than squeeze. Over the life of the filter the flow rate will slow as the membrane gradually fills with particles. Replace the cartridge whenever it feels appropriate.

What contaminants does the filter remove?

The nanofiber membrane targets the reduction of bacteria and protozoan cysts. However, because it is a mechanical filter it will remove all kinds of other particulate matter from your drinking water. Please see the filtration chart in the Whitepaper download for further details. The activated carbon element greatly reduces chlorine present in the input water.

Does Naked Filter reduce chemicals that might be present in the water?

We are targeting removal of bacteria, protozoan cysts and chlorine. The filter is not effective against other forms of chemicals.

To what extent does the filter reduce chlorine?

Our testing demonstrates reduction of chlorine to below taste threshold.

Is it safe to use Naked Filter in the developing world?

Generally yes. Bacteria and protozoan cysts cause the vast majority of waterborne illness around the world. However, the current model of Naked Filter does not remove viruses from water. There is a risk, though unlikely, of viral contamination in any water source.

What is the pore size of the filter?

0.2 micron equivalent.

Do the nanofibers break off or dissolve into the water? Will I be drinking nanofibers?

The materials will not dissolve in water. The fibers are extremely long, mechanically strong, flexible and entangled with each other and therefore will not break off. You will not be drinking these fibers.

Have you done 3rd party testing on this product?

Yes. Our nano-fiber membrane has been shown to conform to EPA requirements for bacteria retention (99.9999% / 6 log reduction) in independent laboratory tests. Please see a copy of the test report here.

Does the filter remove fluoride?

No. For further information about treatment methods for fluoride see here.


I live outside the U.S. What should I know about customs, duties and taxes?

You may be subject to import taxes, customs duties and fees which are levied once a shipment reaches your country. Please keep in mind your Naked Filter order charge only includes 1) the cost of your order and 2) the shipping fees. International shipments will be sent under incoterm DDU. This means you, the customer as the importer, will be responsible for any import duties and fees. These fees vary greatly from country to country and can be expensive so please consider that before making your purchase. In rare situations, customs officials may choose to do random inspections, which can cause a delay (Naked Filter has no control over these charges or delays and cannot predict what they may be). For more information on import duties, we have found these two websites to be helpful: and

Where do you ship from?

Alameda, California — our laboratory, manufacturing, assembly and office facility is located in lovely Alameda, next to Oakland and across the Bay from San Francisco. It's a beautiful quiet community filled with rose gardens and grand old Victorian homes.

Will I be able to track my order?

Yes, once your order ships, you will receive a shipping confirmation email with a link to the USPS tracking information.

How much does shipping cost?

Please use our Shipping rates calculator that is shown at the bottom of the page in the Shopping Cart page. You can use this to get a specific estimate based off your country, state/province and postal code. 

What countries do you ship to?

We currently ship to anywhere USPS will deliver, which is basically everywhere, so feel free to order.